Speech Synth Keyboard -Updated: January 25, 2003

Overview

I've been planning on working on an embedded design project for quite some time, and I've finally settled on one. The basic premise is to interface a computer keyboard with a microcontroller and a speech synthesizer chip in order to create a computer voice. My intent for the keyboard is mainly for musical purposes, and I'm most likely going to create a menu to reflect this purpose. It could, however, also be used as a portable device for the speech impaired. Below is a really really basic block diagram of the system showing the main components.

The five main components are: LCD, microcontroller, keyboard, voice synth ic, and code-to-speech processor. Actually a few other component that could be considered somewhat major are the low-pass filter and the audio amp at the output (I'll explain these in more detail later). So, in theory, once I have all of these pieces combined the user should be able to type something into the keyboard, have the phrase pop-up on the LCD in realtime, and then hear it said by the chip. I also have plans for a menu, giving the user options to store phrases in memory, have the phrase repeat at a specified interval, etc. These will only be added once it is verified that the device works correctly with a basic functionality. The added components will most likely be mounted onto the keyboard in place of the number pad (assuming that all of this circuitry will fit there easily). Since I don't think I'll be making more than one of these and I'm too lazy to layout a circuit diagram, this project will most likely be done on a blank board. Frankly, I see this turning into a big mess.

Components

Microcontroller
The PIC18F452 is one of Microchip's latest microcontrollers and it is incredibly powerful (Probably a lot more powerful than what I'm going to use it for in this current iteration of the project). I chose this chip because I am familiar with it, and it has potential for me to add more to this project later on. I believe you can get these chips at Digikey, or you can get a free sample from Microchip.

Voice Synth and Code-to-Speech ICs
The SPO256-AL2 is a remake of an old speech synth chip sold through Radioshack. It is one of the most commonly used chips in applications like this, making it easy to find info on it. It has 69 allophones (speech sounds) and 5 different pause lengths. The CTS256A-AL2 is a code to speech processor that is loaded with pronunciation rules so when you type in a word the speech chip will pronounce it correctly. Honestly, I'm not sure how well this works, and I may end up not even using it. The only place I could find these chips was at SpeechChips.com. Oh, and I found this datasheet with supplied even more useful info ont eh SPO256-AL2.

Other Stuff
To save money, I tried to recycle old parts and get stuff surplus. The keyboard I already had, and the LCD (which is even backlit) I got surplus online. I just made sure that the LCD used the HD44780 controller chip since its an industrial standard and easy to set up.

Progress

So far, I've managed to scrounge up all of the main components for the project. Since this is my first attempt at a true stand-alone application, I'm still learning about common components that are required, such as shift registers and crystals. In fact, I finally ordered these parts (I'm praying I'll get the right ones), and once these arrive things should be under way again.

I have made some progress otherwise. Typically, I like to see each part of a project work as I go along. Since the datasheets are somewhat cryptic to me on the elements of this project, I chose to get the SPO256 up and running on its own before proceeding with anything else. I found a stand alone configuration for the SPO256, and managed to wire it up. Low and behold, it came to life. Unfortunately, you can't do much with the chip on its own other than get it to make one allophone at a time. It was enough assurance for me at least that the project was feasible. Below is a picture of this messy circuit assembled on my breadboard.

I've also ordered some smaller caps to reduce the mess a bit. I've also ran across someone that actually sells a small pcb for the SPO256 chip. It isn't really optimized for use with the CTS chip, but I've been assured that it has solder pads for hooking it up. SpeechChips.com also has a pcb out which supposedly won't support the CTS at all, but I'm still looking into possibly modifying it.

That's about all I can do for now, other than keep on researching possible methods of improvement, so until my shipment arrives....

More Projects

Video Games

As you may or may not know, Matty Boy Anderson and I have chosen to take on the extrordinary undertaking of creating video games for the masses, with absolutely no compensation other than the joy it may bring to others. Using the immence power of Flash MX, we're currently tackling a few different ideas. In fact John's Arm in: Waka-Atak has been released in beta form (good ol' version 0.9). Its a bit glitchy, but I'd call it a wonderful whack-fest. Fun for the whole family. We've got a few other ideas up our sleeves, so we'll keep ya posted (one of which involves BOOBIES!!!).

Recycling Useless CD's

This project all started when I, as well as everyone else in the house, kept receiving those wretched CD's from, you guessed it, AOL. In stead of throwing away these useless hunks of plastic, we decided to do some wall-papering with them. As of now half of the stairwell of our house is plastered with CD's. When I actually get around to it, I'll take some pictures to illustrate this masterpiece.